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Full text of "Handbook Of Chemical Engineering - I"

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332
CHEMICAL ENGINEERING
passed through the compartment screens while the sub tests were being made and the tailings made during them. The bed top is the material remaining on the jig screens after the last bed was skimmed following the completion of the last sub test.
Product	Dry weight pounds	Per cent weight	Assay			Recoveries,   percentages		
			Silver, ounces	Lead, per cent	Zinc, per cent	Silver	Lead	Zinc,
Feed               ........	2.453H 393K ^y2 95}£ 1,644 221%	100. 00 16.05 4.01 3.89 67.01 9.04	3.14 7.36 1.64 2.40 1.86	0.188 0.644 0.06 0.43 0.078 no assays	0.250 0.798 0.23 0.45 0.137	37.16 2.10 2.97 39.48 17.84	56.74 1.30 8.91 27.83 5.22	51.22 3.75 7.01 36.70 1.31
All  beds ............								
Last bed top .......... Hutches ..............								
Tailings								
Unaccounted ........								
Totals  ............								
	2-.453H	100. 00				100. 00	100. 00	100.00
								
The assay of the different beds of the sub tests as to silver were:
	Test 40, silver, ounces	Test 41, silver, ounces	Test 42, silver, ounces	Test 44, silver, ounces
Bed compartment 1 ......	17.60	18.60	14 40	8.60
Bed compartment 2 ........	8.72	4.00	7.60	5.00
Bed compartment 3	6 24	4.00	5 80	5 92
Bed compartment 4.	4 28	3.96	4 68	3 60
Bed compartment 5 ........	6.96	3.08	5 44	5.60
				
8"
300
2005
The net area of the screen compartments was 11 by 16 in.    The depths of the beds were respectively from compartment one to five, 6 in., 5 in., 4^ in., 4J£ in., 4J^ in.
The respective strokes of the plungers were 1M in., !Ke in., 1% in., 1^6 in., IK in., the number of strokes 175 per minute. Jig practice where the lead content in tailings is reduced to 0.5 to 1.5 per cent lead is considered good.
Working Data for Harz Jigs.—A Harz jig of the type commonly used in Western ore mill is shown in Fig. 3. The proper length of stroke and the proper number of strokes for various sized grains is shown by the curve Fig. 4. For extra close work and in lack of other data the capacity of a jig in tons per 24 hours per square inch of screen surface may be taken as low as (d)^ /100, where d is the average diameter of grain fed in millimeters. For roughing work and on
easy problems the capacity figure given by this formula may be greatly exceeded. It may run to as high as (d)^/20. The average capacity is nearer to the last figure.
t
100 8
0  .25 .50 .751.01.251.501.752.02.252.50
Maximum size of grains-inch. FIG. 4.—Grain-stroke ratio in jigging.